DE 43 34 582 A1 discloses a reel changer in which the action of reaching the position of the carriage bearing the wound reel is determined by means of a laser that can be moved and is arranged above the sliding platform. For this purpose, the laser is moved to the position calculated for the carriage by the computer of the reel changer, the leading edge of the carriage being registered by means of the laser when the calculated position is reached and, at the same time, a signal being sent to the computer of the reel changer to the effect that the carriage has reached the calculated position.
The laser is arranged externally at a distance from the carriage, so that some inaccuracy in this optical position determination cannot be ruled out.
The disadvantage is that, as the carriage is being moved into the sliding platform, nothing is known about the current position of the carriage. It is, therefore, unknown how accurately or at which precise point the carriage is located on the sliding platform. A further disadvantage is that the laser has to be arranged such that it can be moved.